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AAPG Bulletin


AAPG Bulletin, V. 87, No. 5 (May 2003),

P. 817-846.

Copyright copy2003. The American Association of Petroleum Geologists. All rights reserved.

Geochemical characteristics and correlation of oil and nonmarine source rocks from Mongolia

Cari L. Johnson,1 Todd J. Greene,2 David A. Zinniker,3 J. Michael Moldowan,4 Marc S. Hendrix,5 Alan R. Carroll6

1Department of Geological and Environmental Sciences, Building 320, Stanford University, Stanford, California, 94305-2115; current address: Department of Geology and Geophysics, University of Utah, 135 South 1460 East, Browning Building, Salt Lake City, Utah, 84112-0011; email: [email protected]
2Department of Geological and Environmental Sciences, Building 320, Stanford University, Stanford, California, 94305-2115; current address: Anadarko Petroleum Corporation, 1201 Lake Robbins Drive, The Woodlands, Texas, 77380
3Department of Geological and Environmental Sciences, Building 320, Stanford University, Stanford, California, 94305-2115
4Department of Geological and Environmental Sciences, Building 320, Stanford University, Stanford, California, 94305-2115
5Department of Geology, University of Montana, Missoula, Montana, 59812
6Department of Geology and Geophysics, University of Wisconsin, Madison, 1215 W. Dayton St., Madison, Wisconsin, 53706


Cari Johnson is an assistant professor at the University of Utah. She received geology degrees from Carleton College (B.A., 1996) and Stanford University (Ph.D., 2002), where she also completed postdoctoral research on sequence stratigraphy of the San Joaquin basin. Her dissertation focused on the sedimentary record of Late Mezosoic extension in the China–Mongolia border region. She continues to conduct research in basin analysis, sedimentation and tectonics, and petroleum geology in east-central Asia and western North America.

Todd Greene attained a B.S. degree in earth sciences from the University of California at Santa Cruz (1994) and a Ph.D. in geological sciences at Stanford University (2000). His dissertation focused on tectonics, sedimentology, organic geochemistry, and petroleum systems of the Turpan-Hami basin of northwestern China. He is currently employed by Anadarko Petroleum in Houston, Texas, where he is part of a regional studies team investigating basins and play types in the greater Rocky Mountains.

David A. Zinniker is a Ph.D. candidate in the Department of Geological and Environmental Sciences at Stanford University. His research focuses on molecular fossils of plants and algae and their bearing upon ecology, evolution, depositional systems, and petroleum geology. His future projects include using molecular and macromolecular markers to study current ecological processes and events deep in geologic time.

J. Michael Moldowan attained a B.S. degree in chemistry from Wayne State University, 1968, and a Ph.D. in chemistry from the University of Michigan in 1972. Following a postdoctoral fellowship in marine natural products with Professor Carl Djerassi at Stanford University, he joined Chevron's Biomarker Group in 1974. Moldowan joined the Department of Geological and Environmental Sciences of Stanford University as professor (research) in 1993.

Marc S. Hendrix received geology degrees from Wittenberg University (B.A., 1985), the University of Wisconsin, Madison (M.S., 1987), and Stanford University (Ph.D., 1992). He completed postdoctoral research at Stanford in 1994 and since has been a professor of geology at the University of Montana, Missoula. His research interests include sedimentary basins and paleoclimate studies, particularly in western North America and central Asia.

Alan Carroll conducts research on large lake basins in Asia and the western United States, focusing on their tectonic setting, sequence stratigraphy, and petroleum potential. He worked for three years as an exploration geologist for Sohio, and five years for Exxon Production Research. He is currently an associate professor at the University of Wisconsin.


We thank D. Badamgarav, G. Badarch, R. Barsbold, D. Janchiv, and our other colleagues at the Mongolian Academy of Sciences, Institute of Geology and Mineral Resources, the Petroleum Authority of Mongolia, and the Mongolian Paleontological Institute for their scientific and logistic support. Funding for this study was provided by Roc Oil, the Stanford Graduate Fellowship, the International Research and Exchange Board, the Stanford-Mongolia Industrial Affiliates program, and by National Science Foundation grants EAR-9708207 and EAR-961455 to S. Graham and M. Hendrix, respectively. S. Graham was a principal advisor on this and related projects in Mongolia and offered much insight throughout this study. Colleagues at various labs assisted with sample analysis, including K. K. Bissada (Houston Advanced Research Center), H. Hada (Micropaleoconsultants), and Zhengzheng Chen, D. Mucciarone, and F. Fago at Stanford University. Additional bulk geochemical analyses were completed at ExxonMobil Upstream Research (formerly EPRC). We thank P. Albrecht and P. Adam for discussion and supporting data on polycyclized polyprenoids and E. Chang (Stanford University) for the Chinese oil samples. J. Amory, M. Beck, L. Lamb, R. Lenegan, D. Sjostrom, E. Sobel, and L. Webb provided additional assistance in the field. Reviews by M. Fowler, K. Peters, and Wan Yang greatly improved this manuscript.


New bulk and molecular organic geochemical analyses of source rock and oil samples from Mongolia indicate the presence of lacustrine-sourced petroleum systems in this frontier region. Samples of potential source rocks include carbonate, coal, and lacustrine-mudstone lithologies that range from Paleozoic to Mesozoic in age, and represent a variety of tectonic settings and depositional environments. Rock-Eval and total organic carbon data from these samples reflect generally high-quality source rocks, including both oil- and gas-prone kerogen types, mainly in the early stages of generation. Bulk geochemical and biomarker data indicate that Lower Cretaceous lacustrine mudstone found in core from the Zuunbayan field is the most likely source facies for the East Gobi basin of southeastern Mongolia. Oil and selected source rock samples from the Zuunbayan and Tsagan Els fields (both in the East Gobi basin) demonstrate geochemical characteristics consistent with nonmarine source environments and indicate strong evidence for algal input into fresh- to brackish-water source facies, including elevated concentrations of unusual hexacyclic and heptacyclic polyprenoids. Despite similarities between Zuunbayan and Tsagan Els oil samples, biomarker parameters suggest higher algal input in facies sourcing Zuunbayan oil compared to Tsagan Els oil. Tsagan Els oil samples are also generated by distinctly more mature source rocks than oil from the Zuunbayan field, based on sterane and hopane isomerization ratios.

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